This volume describes the role of cancer stem cells and progenitor cells in the progression to cancer. The reviews cover the gamut of tissue types and cell lines as well as differentiate between normal cells and tissues and those that become cancerous. It is the editor’s hope that by examining the role of these self-renewing cells novel therapeutics can be developed. Contributors have attempted to provide an overview of the developing concepts and controversies in the area of stem cell biology as it relates to the formation of cancer in various tissue types. Specifically, the investigators refer to the role of stem cells in well-characterized diseases such as prostate and hepatocellular cancer, melanoma, chronic myeloid leukaemia and stem cell/cancer stem cell properties. Also the Wnt pathways have been examined, next to stem cell lineage, and characteristics of specific stem cell biomarkers. This book attempts to shed light on some of the current stem cell researches as well as place an emphasis on potential targets for therapeutic focus in these diseases. Multiple systems and tissues are reviewed because of their involvement in extensive studies of stem cell biology, which could potentially become a model for other fields of research.